A master talks to a slave. Each unit has a master and a slave address register. Only one device can talk on the bus at any given time. There is a pecking order for the types of communications which will take precedence over another. Each communication from master to slave must be replied to by the slave going back to the master with an ACK (acknowledge) bit. If the master does not receive the ACK within a predetermined time allowance it drops the communication and returns to its standby (listen) mode.

The µPD6708GT (-a appended for the leadfree) processes the protocol of the IEBus. Because it is provided with a transmit/receive buffer, the microcontroller can concentrate on the application processing of the IEBus. Because the µPD6708 also contains an IEBus driver/receiver, it can be directly connected to the bus. link

The µPD72042BGT (-a appended for the leadfree) performs all the processing required for layers 1 and 2 of the IEBus. The device incorporate large transmission and reception buffers, allowing the microcomputer to perform IEBus operations without interruption. They also contain an IEBus driver and receiver, allowing them to directly connected to the bus directly. link

The M16C MCU Platform of products offers you a variety of choices, spanning entry-level capabilities and pricing previously associated with 8-bit MCUs; hitting many options of pin-count, RAM and ROM choices; and reaching into the high-speed processing of 32-bit MCUs — all with MCUs that are upwardly pin- and software-compatible. For communications these chip have optional clock synchronous/asynchronous shared (max 5 channels), IEBus (max 5 channels), I2C bus (max 5 channels), CAN 2.0B (max 2 channels). The only group in this family which does not have the IEBus functionality available is, the M16C/70 group. link

Fujitsu MB90580 - The MB90580/85 series has peripheral resources of an IEBus controller.

Marcin's Site - This site is great for learning more about the IEBus! He has really done a great job researching this protocol as well as developing one of the first boards that can talk on the bus using an ATMEGA8. (there are active forums on his site too, here).

Louis Frigon (SigmaObjects.com) - A great write-up with schematics and source code that interfaces with the IEBus to trick the stock head unit into enabling aux input as it would for a CD changer. It is a great learning tool for how the IEBus protocol works just by looking through the well commented firmware source code. (Adapted from work done by Marcin at his site.